Solution concentration indicator



Nov. 7, 195% A. L. KOHL SOLUTION CONCENTRATION INDICATOR Filed Nov. 25,1946 FIG.

FIG.

FIG. 3.

TEMPERATURE DEG.

INVENTOR ARTHUR L. KOHL ATTORNEYS Patented Nov. 7, 1950 SOLUTIONCONCENTRATION INDICATOR Arthur L. Kohl, Los Angeles, Calif., assignor toTurco Products, Inc., Ls Angeles, Calif., a corporation of CaliforniaApplication November 23, 1946, Serial No. 711,980

1 Claim.

The present invention relates to an electronic indicator, and moreparticularly to a device for indicating when a predetermined minimumconcentration of a solution has been attained.

In many types of solutions, for example saline and alkaline .solutions,their conductivity is a function, when corrected for temperature, of thedegree of concentration of the solution. This fact is well known and hasbeen the basis for solution concentration indicators. Such previousdevelopments have employed, for example, indicating instruments such asvolt meters and the like connected either in parallel or in series witha circuit path through the solution to be tested, to indicate therelative conductivity and thereby the degree of concentration of thesolution. These previous developments are useful in laboratory work,where an operators principal duty consists in observing the position ofthe indicators on the instruments and making necessary corrections inaccordance therewith. However, in commercial operations, for examplemachine dishwashing in restaurants and the like, the operator frequentlyis concerned only with his principal task of washing dishes. In suchcases, the provision of a dishwashing machine with an ordinary type-ofsolution concentration indicator is of little or no value, sincepersonnel normally employed to wash dishes are not of the type which canbe depended upon to observe ordinar indicating mechanisms and be guidedby their indications.

An object of the present invention is to make an improved and simplifiedsolution concentration indicator.

Another object is to make a solution concentrationindicator having anelectric circuit which includes a predetermined conductive path througha solution to be tested together with an electronic glow lamp which isadapted to glow at and above a predetermined critical value, the circuitincluding current control means which may be adjusted to predeterminedsolution concentration and temperature compensation.

Another object is to make a solution concentration indicator having anelectric circuit with a relatively high voltage primary portionembodying an electronic glow lamp which is arranged to glow on theattainment of a predetermined condition in its circuit, the glow lampcircuit having electrical control means calibrated in accordance withsolution concentration and temperature compensating requirements; and acoupled secondary circuit of substantially lesser voltage, whichincludes a predetermined electric current path through a solution to betested.

These and other objects of the invention will be set forth more fully inthe following description and the accompanying drawings, comprising onesheet. In the drawings:

Fig. 1 is a schematic circuit drawing of a solution concentrationindicator embodying the present invention; I

Fig. 2 is a similar schematic drawing of a modified form of solutionconcentration indicating circuit; and

Fig. 3 is a double compensating control for controlling a currentregulating device in accordance with solution concentration andtemperature compensation requirements.

Referring to the drawings in detail, It) represents a tank, for examplethe solution tank of a dishwashing machine, in which a quantity ofdishwashing solution II is contained. A pair of contact members I2 andI3 are mounted in the tankso as to be immersed in the solution in asuitable manner. The exposed surfaces of the contact members l2 and I3are of suitable electrically conductive material toresist corrosion bythe solution with which they are to be used. The contact members areconnected, by conductors l4 and I5, respectively, to the terminals of asecondar coil l! of a transformer iii.

A primary coil IQ of the transformer I8 has one terminal thereofconnected to a conductor 20, which is connected, through one side of atwo pole switch 2 l, to a conductor 3| comprising one side of anelectrical supply line. The line may be energized with ordinary 115volt, cycle current. The other terminal of the primary coil I9 isconnected by a conductor 23 to the slide, or

arm, 24 of a variable current control device such tion to be employed,and the amount of resistance used would be compensated or changed if asolution having different current-concentration characteristics were tobe employed. I

An ordinary low wattage electric pilot lamp 32 is connected byconductors 33 and 34 across the conductors 20 and 30. so that at alltimes A gas filled glow lamp 35, which may be of the neon filled typewhich begins to glow at a predetermined difierence of potential, forexample sixty volts is connected by conductors 31 and 38 through a fixedresistor '39 to the conductors 23 and20. The amount of resistance of theresistor 39 is determined by the characteristics of the,

glow lamp 35, and with some types of glow lamp will be unnecessary.

The variable resistor 25 preferably is controlled by a compensatingdial, as indicated in Fig. 3. In this compensating dial arrangement apointer 40 is secured on a shaft pivoted in, and extending through, adial 4|. The other end of the shaft 40 is secured in=a usual manner tothe arm or slide 24 of a rheostat of predetermined resistancecharacteristics. The dial Al is pivoted on a usual type of insulatingpanel such as is used in electrical calibrating equipment. The dial 4|,as illustrated, has a point projecting radially from its periphery, andlines are scribed on the panel indicating proper positions of this pointto compensate for solution temperatures of 120, 130 and 140 degreesrespectively. This covers the temperature range required for dishwashingmachines for which the illustrated embodiment of the device is intended.

The margin-a1 area of the dial has a scale imprinted thereon whichindicates concentration characteristics of the solution. By setting thepoint on the dial to indicatethe temperature of the solution, and thensetting the pointer 159 on the dial scale to indicate a desired solutionconcentration, the rheostat wiper 24 will be set at a predeterminedpoint. This point is calibrated to provide the required amount ofresistance in the primary circuit to cause an ionized flow of currentthrough the lamp 35 to light'the lamp when the concentration of thesolution and thereby its conductivity, increases beyond the amountindicated on the dial scale.

Instead of the compensating device illustrated, separate variableresistor may be employed if desired to compensate for temperature andconcentration characteristics separately.

The operation of the circuit shown in Fig. 1 is as follows: When thecircuit is connected to the line by closing the line switch 2|, thepilot light 32 will be lighted, since it is connected directly acrossthe line. Assuming that the degree of concentration of solution in thetank I is extremely low, and that the resistance across the contactmembers 12 and I3 is, therefore, comwill tend to fiow from the conductor25 on one side of the line, through the conductor Bl, the gas filledglowlamp 35, the fixed resistance 39 and the conductor 38 to theconductor 23 on the other side of the line.

If the impedance of the primary coil is suili ciently high and thecombined resistances of the fixed resistor 26, ti -e variable resistor25. is s'ufiiciently low, the potential difference through the glow lampwill ionize the gas therein to a point which will cause the lamp toglow. These factors are predetermined so that the glow lamp 35 will glowwhen the solution strength drops below the required minimum asdetermined by the setting of the pointer illand dial 4 I.

If the concentration of the solution, and there-- fore its conductivity,is increased, a greater flow of current will of course occur in thesecondary circuit. This increased flow of current in the secondaryreduces the impedance eiiect in the primary coil and therefore permits agreater flow of current through the primary coil. This increased flowthrough the primary coil tends to shunt the current from its previouspath through the glow lamp. When the difference in potential across theglow lamp thus is reduced an amount determined by the setting of thedial M, the pointer 40 and the increased conductivity of the solution H,the glow lamp 35 will'be deionized and will cease to glow.

This arrangement whereby the glow lamp is illuminated only when theconcentration of the solution is below a predetermined minimum isdesirable, since dishwashingpersonnel are in-- clined to increase thestrength of the solution far beyond that necessary forsatisfactory'operation of the dishwashing machine. With the arrangementillustrated in Fig. l, the glow lamp 35 will be illuminated onlywhen'the concentration of the solution is below that determined by thesetting of the concentration indicator ll? and terpreted to indicate thesolution concentration.

In the circuit shown in Fig. 2, a pair of contact terminals and 5!,which may be of the same type as those illustrated in Fig. l, arearranged to be immersed in a solution 53 in a tank 52. These contactterminals are connected, by conductors 54 and 55, to opposite sides of acircuit, for example a 115 volt, 60 cycle circuit. A variable resistor51 is mounted in the conductor 55 and may be controlled by suitabl meanssuch as a pointer 40 and dial H similar to that illustrated in Fig. 3. Aglow lamp 53 is connected in parallel with the contact terminals 50 and5!, by means of conductors 59 and Gil, which are connected respectivelyto the conductors 5G 55. i

In the circuit illustrated in Fig. 2, the glow lamp 58 will beilluminated when the resistance between the contact member 55 and iii issuiiiciently high to produce an adequate drop in potential across theglow lamp. When theConmined minimum requirement, the lamp 58 will beextinguished.

In both circuits illustrated in Figs. =1 and 2- it is consideredpreferable to have the controls for the variable resistance'unitsmounte'd. within a cabinet or otherwise concealed so as not tobereadily available to the dishwashin'g person- By this arrangement theproprietoror nel. manager of the establishment. can set the, con

, trols for the required degree of concentration and temperature. Thedishwashing personnel and then merely will be instructed to addsufiicient powder or concentrate to extinguish the glow lamp when it isilluminated. The addition of powder or concentrate when the lamp is notilluminated may be prohibited. By placing the glow lamp in a positionwhere it is visible to supervisory personnel as well as to the operatorsof the dishwashing machine, wasting of the material may be prevented orat least substantially reduced, while at the same time insuring that asolution of adequate concentration is being employed.

While I have illustrated and described a preferred embodiment of myinvention and one modification thereof, it will be understood by thosefamiliar with the art that these showings are illustrative only, andthat the device is capable of modification without departing from thespirit of the invention. It is desired, therefore, not to limit theinvention except as defined in the following claim.

I claim:

A solution minimum concentration indicator comprising, in combinationwith a tank adapted to contain a solution; a primary electrical circuit,a secondary circuit having electrical induccharacteristics shunt-mountedin the primary circuit, and variable current control means mounted inthe primary circuit to vary shunt operation of the lamp whereby thedifference in current potential across the lamp shunt comprises afunction of current flow in the secondary circuit, including currentflow in the solution between said contact terminals, a fixed memberpresenting calibrated temperature indicia, and a dial, mounted to rotaterelative to said member carrying a pointe for selective registrationwith said indicia and carrying indicia calibrated in percentages ofsolution concentration units, and a pointer operativel connected to saidvariable current control means, said pointer bein movably mounted forselective registration with the last named indicia.

ARTHUR L. KOHL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,996,063 Corkran Apr. 2, 19352,068,499 Mackenzie Jan. 19, 1937 2,221,307 Christie Nov, 12, 19402,224,382 Douty Dec. 10, 1940 2,290,574 Shafer July 21, 1942

